1. Field of the Invention
This invention relates to cleaning compositions which will replace cleaning agents containing an organic solvent including flon and the like.
2. Description of the Related Art
In manufacturing various parts such as metal parts, plated and coated parts, and electronic and semiconductor parts, flon containing solvents such as flon 113, and organic solvents such as trichloroethane, trichlorethylene, tetrachloroethylene, and carbon tetrachloride are widely used as cleaning agents for eliminating oil stains and the like.
The above organic solvent containing cleaning agents are also used as dewatering cleaning agents after having washed various parts with water in order to avoid the following problems that are associated with direct drying of water present on an object to be cleaned:
(1) Heating (100.degree. C. or more) which entails energy loss; PA1 (2) Reducing in productivity due to time taken in drying; PA1 (3) Likely deformation of the object to be cleaned due to heating (thermal expansion that exceeds the tolerance); and PA1 (4) Increase in space for installing a cleaning system including a cooler and a heat shielding unit.
The term "dewatering cleaning agent" is used herein to denote a cleaning agent into which an object to be cleaned, which has been washed with water, is immersed or with which the object is rinsed by shower thereby to have water present on the object substituted by itself and then vaporized by air at room temperature or heated to 60.degree. C. or less so that the object can be dried.
However, ever since it has been found that the destruction of the ozone layer by discharge of flon affects seriously the human body and the ecological system, the use of flons such as flon 12 and flon 113 whose ozone destruction coefficients are high is on the gradual decline on a global scale for an eventual total ban.
Stricter regulations are imposed also on chlorine containing organic solvents such as trichloroethylene and tetrachloroethylene which are presumed to induce soil and underwater contaminations and the like.
Flons whose ozone destruction coefficients are lower than the currently used flon containing solvents are being developed, some of which are under fabrication on a commercial basis. However, these new developments are not so welcome because they still are destroyers of the ozone layer.
What gradually attracts attention as a replacement for the above organic solvents is a surfactant-based water system cleaning agent which is free from environmental destruction and contamination. However, cleaning agents containing only surfactants are not satisfactory in penetrability, thereby not cleaning, e.g., stains penetrated into narrow portions and medium to high viscous, persistently sticky oil stains.
Japanese Patent Publication No. 50463/1988 discloses a method of cleaning woven materials by using silicone containing compounds. According to the disclosure, a liquid cleaning composition containing an effective amount of cyclic siloxane having 4 to 6 silicon atoms is used. However, the liquid cleaning compositions including the above silicone containing compound are not suitable for use not only in general industrial products due to their being specifically prepared for woven materials, but also in systems using water (hereinafter referred to as "water system") due to their being based on a single cyclic siloxane or the mixture of a cyclic siloxane and an organic solvent. Further, such compositions are not so dispersive in water that the addition of a surfactant thereto does not assist in blending them homogeneously, thereby causing phase separation immediately. Thus, they are not adapted for use as water system cleaning agents.
On the other hand, Japanese Patent Laid Open No. 56203/1978 recites an aerosol aqueous cleaning composition containing a chain polydimethylsiloxane having 2 to 3 silicon atoms in a single molecular. Since its content is limited to about 0.02 to 0.1 wt. %, no such advantage as improving the cleaning property of water system cleaning compositions is disclosed.
Under such circumstances, the development of high-performance water system cleaning agents free from environmental problems is strongly called for.
In the meantime, the use of lower alcohols such as isopropyl alcohol is under study for a new development that can replace the above-mentioned organic solvents for dewatering. However, isopropyl alcohol has a flash point of 11.7.degree. C., which is lower than room temperature, and this involves some danger of fires under ordinary handling conditions. In addition, isopropyl alcohol is highly compatible with water, so that the initial dewatering property is ensured, but its repetitive use causes dissolved water to be present again. As a result its dewatering property will be impaired on a long-term basis. To refine isopropyl alcohol for reuse by removing water from the water containing isopropyl alcohol, a tremendous equipment investment is required. That isopropyl alcohol is toxin to the human body is another factor that tends to keep it from using.
The use of hydrocarbon and higher alcohols which have higher flash points than room temperature allows a comparatively easy removal of water, but their low volatility prevents drying themselves at low temperatures, e.g., 60.degree. C. or less, thereby making them unsuitable for applications to dewatering cleaning agents.
Therefore, an object of the invention is to provide water system cleaning compositions which have cleaning capability equivalent to that of organic solvent containing cleaning agents including such as flon and which are stable as water system cleaning agents and free from environmental destruction and contamination.
Another object of the invention is to provide dewatering compositions which have the substituting and drying properties equivalent to those of organic solvent containing dewatering cleaning agents, which have few risks of fires and which are free from environmental destruction.